Combination of projection-based XRF, XAFS and XRD imagings for rapid spatial distribution analysis of a heterogeneous material

Abstract

A projection-based X-ray imaging method with a millimeter-scale sampling region was applied to multiple X-ray analysis of a multicomponent mixed sample. XRF (X-ray fluorescence) images were obtained by irradiation with monochromatic synchrotron X-rays, and the elemental distribution of iron on the sample surface could be obtained with a resolution of several tens of microns. XAFS (X-ray absorption fine structure) spectra were obtained by collecting XRF images by irradiation with X-rays around the Fe K absorption edge, and the spectral features were compared for three iron oxides. Differences in the oxidation state and coordination number around Fe for three different oxides could be identified based on shifts in the absorption-edge and the pre-edge structure, respectively. An XRD (X-ray diffraction) image could be observed when the incident energy satisfied Bragg's condition of any one plane in an oxide. Each oxide was completely discriminated, and differences in the crystallite size were confirmed from the XRD images. This imaging procedure can provide information on the spatial distribution of elements, as well as their chemical states and local atomic configurations on an intermixed surface within several tens of minutes. Using this multiple X-ray imaging method, direct analysis of various materials should be possible, facilitating elucidation of the characteristic properties or chemical phenomena of complex and heterogeneous samples.